NO. 8 ANATOMICAL LIFE OF THE MOSQUITO SNODGRASS 39 



Salem (1931) forms a distinct lobe below the mouth (fig. 15 A, Hphy, 

 L b), as it does also in a tipulid larva (fig. 7 A). The rudiment of the 

 pupal labium within the larval labium (fig. 15 A, pLb) is said by 

 Imms (1908) to be a pair of hollow lobes confluent at their bases. 

 There is no separate rudiment of the adult hypopharynx. It is shown 

 by Thompson (1905) that the hypopharynx is still united with the 

 pupal labium (fig. 15 B) when the larval cuticle (ICt) is moulted. 

 Later, as will be described, the hypopharynx of the adult female is 

 separated from the labium. In their final stage of development the 

 pupal mouth parts have become greatly lengthened and are closely 

 pressed together in a long curved proboscis (D). 



Rudiments of the pupal tail fins are formed beneath the cuticle of 

 the fourth larval instar behind the respiratory apparatus, and the 

 primary buds of the male external genital organs appear beneath the 

 cuticle of the same instar behind the sternal region of the ninth 

 abdominal segment. 



THE MATURE PUPA 



The pupa at ecdysis (fig. 16 A) is fully formed in all its outer parts 

 and thereafter does not change externally. It is clearly a preliminary 

 adult with the appendages in a halfway state of completion. The pupa 

 can hardly represent a former active stage in the life of the mosquito, 

 since its mouth parts are unfitted for any kind of feeding. The pupal 

 thorax has already assumed the approximate size and shape of the 

 adult thorax. In Simuliidae, Hinton (1959) says, the definitive 

 thoracic structure is developed during the pharate stage of the pupa. 



General external structure. — The head and thorax of the mosquito 

 pupa are combined in a large cephalothorax, from which projects the 

 slender abdomen (fig. 16 A). When at rest the pupa floats at the sur- 

 face of the water (fig. 13), but it does not hang from its respiratory 

 trumpets (as it often does in pictures). The back of the thorax and 

 of the two anterior abdominal segments comes against the water, 

 while the rest of the abdomen hangs downward as ballast. The open 

 ends of the respiratory trumpets project just above the surface of the 

 water, and two small brushes of spreading hairs on the back of the 

 first abdominal segment help keep the pupa suspended. The floating 

 position of the pupa is necessary for the future emergence of the 

 adult, and is maintained by bubbles of air enmeshed in the folds of 

 the legs and beneath the wings. 



The source of the air that maintains the buoyancy of the pupa, 

 according to Hurst ( 1890) , appears to be a pair of large open spiracles 



